Field of the Invention
This disclosure generally relates to fiber optic connector inspection, and more particularly to microscopes used to inspect multifiber connectors.
Background of the Invention
Fiber optic links are key elements in many local and wide area digital broadband networks. However, even micron-sized dust particles or defects in the endface of a fiber optic connector can cause a link to fail. Thus technicians who install or maintain fiber optic equipment or cables in the field, as well as associates who perform assembly or quality assurance functions at facilities that manufacture fiber optic equipment or cable assemblies, are normally required to inspect the endface of every fiber optic connector before it is mated with another connector.
A wide range of single-fiber and multiple-fiber connector types are in use today. A popular multiple-fiber connector type called “MPO” is available in versions that can terminate from 12 to 72 individual optical fibers. For example, the endface of an MPO 32 connector includes the endfaces of 32 fibers grouped in two rows of 16 fibers each, while the endface of an MPO 72 connector includes the endfaces of 72 fibers, grouped in six rows of 12 fibers each.
Multifiber adapters for single-fiber connector inspection microscopes are disclosed in U.S. Pat. No. 8,104,976 (Zhou et. al.), U.S. Pat. No. 7,239,788 (Villeneuve), and U.S. Pat. No. 6,879,439 (Cassady). However, these systems must be operated manually and therefore may be slow or difficult to use.
An imaging system that could be used to implement adapters that would allow compatible single-fiber microscopes to automatically inspect multiple-fiber connectors, or to implement automatic, multiple-fiber inspection microscopes, is disclosed in U.S. Pat. Appl. 20150092043 (BARIBAULT). However, the preferred embodiment of this system includes one or more servomotor-controlled mirrors, and thus may not meet the reliability, drop-test, or vibration tolerance requirements of some users.
It is also possible to imagine a fiber optic connector microscope able to capture single images that encompass all fibers in the endface of any connector in a specified set of multiple-fiber connectors. Such a microscope could be fast and rugged. But its implementation would require the use of a very large image sensor. For example, as shown in FIG. 1, if we assume a specified set of connectors that includes MPO 32 and MPO 72 type connectors, and add some margin to account for mechanical tolerances, then the total area on the endface under inspection which must be viewable by the microscope, or the minimum microscope Field of View (FOV) 103, would be a rectangle with a horizontal dimension (H) of 4.6 mm and a vertical dimension (V) of 2.1 mm. If we further assume a sensor aspect ratio of 3:2, which is common for high pixel count, large format image sensors, then the FOV of each image captured by the sensor, or the sensor FOV, must also have a width of 4.6 mm, as shown in FIG. 2. If we further assume a microscope resolution requirement of 1 micron, and thus a pixel density requirement of about 2 pixels per micron, then the sensor would must have a total of 4600 um×2 pixels/micron=9600 pixels in the horizontal dimension. Thus the required sensor size in terms of pixels would equal [2/3][9600]2 or about 56 million pixels (Mp). Or if our goal is to match the resolution of current art, single-fiber microscopes, or about 0.5 microns, then a pixel density of 4 pixels per micron may be required. In this case the image sensor would require over 200 million pixels.
Thus, there is a need in the art for an imaging system that may be used to implement multiple-fiber connector inspection microscopes that are free of the disadvantages mentioned above.